Personally I think $300 is WAAY over the top for a 90 gallon. Not only that it's probably custom made and has thin glass since it's cube. As well as the height isn't too much of a good idea. But IMO you should've asked more about the tank then explained your reasoning. Still a little ridiculous how he shut out a potential buyer. But I gues he didn't care to negotiate that much. Personally I bought a 7" Cichla kelberi from Davenmandy for $100 after he decided to lower it from $150. He spent around $200 for it at 3" with shipping etc. You put it at a higher price and narrow down your offers from other potential buyers and wait a little to see the best offer. Anywho getting a little off topic how much did you sell the freshwater moray for listed at $250 davenmandy?